Thread-cutting mechanism for sewing machines



W. C. SHIELD ET AL THREAD CUTTING MECHANISM FOR SEWI'NG MACHINES Dec. 71926.

Jar/bald.

IN VEN TOR.

Filed Sept. 10, 1925 Patented Dec. 7, 1926.

WILLIAM C. SHIELD AND LAWSON THREAD-CUTTING MECHANISM non. SEWINGmaciniinslf Application filed September This invention relates to threadcutting mechanism and particularly to a thread cut- ,ting attachmentadapted to automatically sever the thread connected to a sewed articleas the article passes from the machine.

The present invention is particularly use- 1f ul in connection withcontinuously operating bag sewing machines wherein the bags are passedthrough the machine in succession,

and are all connected by the sewing thread.

\Ve are aware that some devices for performing this function have beenheretofore known and it is therefore the primary objectof our inventionto provide an improved device for this purpose which will operate to:mtomatically sever the portion of sewing thread connected to a sewedarticle as the article passes from the machine.

In accordance with our'invention, we provide a toothed guard and arotary spiral cutting member therein and mount this guard on the rearface of the sewing machine beneath the top sewing surface thereof. Oneedge of the rotary spiral member is sharpened in a manner cooperatingwith sharp cutting edges of the guard. Upwardly extending openings areprovided between the adjacentteeth of the guard whereby when a sewedarticle passes over the guard and drops down by gravity the threadconnected thereto will automatically dropinto one of such openings andbe severed by the sharp edges as the member is rotated. It is an objectof our invention to provide an improved thread cutting mechanism of thistype.

in the accompanying drawing we have shown one specific embodiment of ourinvention. but it will be understood that the invention can be otherwiseembodied and that the drawing is not to-be construed as defining orlimiting the scope of the invention, the claims appended to thisspecification being relied upon for that purpose.

Referring to the figures of the drawing,

Fig. 1 is a rear elevation of a sewing machine having our thread cuttingattachment mounted thereon.

Fig. 2 is a fragmentary plan view thereof showing our invention.

Fig. 3 is an enlarged sectional view through the severing mechanism.

Fig. 4vis a fragmentary end view of the machine.

Fig. 5 is a cross sectional view taken on line VV of Fig. 3.

c. IVY. or cnocxnzr'r, CALIFORNIA.

10. 1925- sci-1a: m. 55,436i

Referring more specifically tothedrawmg by reference characters, 1indicatejs a sewing machine having a sewing portion 2 over a top-sewingsurface 3. I sewed moves in thcdirection otfjthe arrow shown in Fig. 4.

Our invention as illustratedis inthe forin of an attachment adapted tobe d to the rear edge of the machine. T

end blocks a secured to "anipthhediate block 6 by screws 5. Theintermcdiateblock is milled to form a plurality of teethiT witl'iopenings 8 therebetween The opening'in the block 6 wherein the member 4is mounted is such that the peripheral portion off 'the spiral element 9fits accurately thereagainst as illustrated in Figs. and 5. Aswill beThe; article.

I device comprises a member 4 rotatably mounted in noted, the outer edgeface of the spiral memher 9 is relatively wide and cylindrical in shapein a manner cooperating with the wall of the opening in the block 6 toform a bearing for the member 4 and element 9. The member 4 is thereforeassured of true rotation along its entire length and the quick andaccurate cutting of the threads is likewise assured.

The member 4 can be driven from the main shaft 10 of the machine througha belt 11 or by any means desired. As the member 4 is rotated in thedirection of the arrow, the edges 12 which are preferably under-cut tomake a sharp cutting edge,'cooperate with the edges 13 of the teeth 7 aswill be understood. By locating the cutting teeth 7 at the upper portionof the block 6. a suitable length of string is left on the articlesevered as will be seen by referring to Figs. 4 and 5.

It is believed that the operation of the mechanism will be clearlyunderstood from the above description. The sewing bags 14 and 15 areconnected by the sewing thread 16. As the sewing continues, the end bag15 drops over the edge of the guard 7 and the thread 16 thereof into oneof the openings 8. The member 4 being continuously rotated, the sharpedge 12 thereof cooperates with the sharp edge 13 and severs the thread.

It will be noted that the intermediate block 6 and end bearing blocks 5are rigidly secured together by screws which form these parts into aunit attachment adapted to be secured to the rear edge of the sewing ma7 wardly of the block 6 from the rear edge thereof, in a manner formingthe rearward y extending teeth 7. These teeth are located at the top ofthe block, whereby they not only serve to support the sewed articleuntil it tops off the rear edge, but also serve to sever the thread assoon as it enters a recess, even though the article does not drop downto a fully vertical position (see Fig. 4).

Having thus described our invention, what we claim and desire to secureby Letters Patent is- 1. In combination with a sewing machine, a threadcutting mechanism comprising a block secured to the machine rearwardlyof .the sewing mechanism, a plurality of teeth at the top of the blockhaving their free ends extending in a direction away from the sewingmachine, a shaft rotatably mounted in the block and carrying acontinuous spiral cutting tooth cooperating with the said teeth, oneedge of the said tooth being sharp and cooperatin with the said teeth tosever a thread fal mg downward between two adjashaft for rotating thesame.

2. In combination with a sewing machine, a thread cutting mechanismcomprising a block secured to the machine rearwardly of the sewingmechanism, the block being provided with an opening longitudinally centteeth, and means on one end of the therethrough and the to face of theblock being provided with a p urality of recesses extendmg thereintofrom the rear edge thereof, the said recesses forming a plurality ofrearwardly extending teeth the top surfaces of which forma portion ofthe top of the block, a shaft rotatablymounted in the block and carryinga continuous spiral cuttin tooth cooperating with the said teeth,

one e ge of the said tooth being sharp and cooperating with the saidteeth to sever a. thread falling downward into a recess between twoadjacent teeth, and means on one end of the shaft for rotating the same.

3. A thread cutter for sewing machines, comprising the combination of ablock having a cylindrical opening longitudinally therethrou h, aplurality of laterally extending teeth orming a portion of the wall ofsuch opening, and a rotary shaft mounted in the opening and having acontinuous spiral rib thereon having one edge sharp in a mannor toco-operate with the teeth to sever a thread therebetween when the shaftis ro- .tated, the outer edge face of the rib being manner to formabearing for the shaft.

WILLIAM C. SHIELD. LAWSON C. IVY.

